Administration of a single course of corticosteroids to mothers at risk to preterm delivery has conclusively been shown to reduce the incidence of respiratory distress syndrome and neonatal mortality in premature fetuses. Despite inadequate data to establish the clinical benefit beyond 7 days after antenatal corticosteroid therapy, many clinicians routinely repeat courses of corticostedroids on a weekly basis if the patient remains undelivered. The short and long term implications of this pratice are unknown. Our objective in performing this multi-center, randomized placebo-controlled trial of the weekly use of corticosteroids in women at high risk for preterm delivery is to establish the efficacy of this practice compared to single series in reducing the incidence of respiratory distress syndrome and neonatal dealth in premature neonates.